Sequenced initiation-a technique for explosive wave shaping



June 20, 1967 A. SILVIA ETAL 3,326,125

- A TECHNIQUE FOR EXPLOSIVE WAVE SHAPING Filed Sept. 20, 1965 SEQUENCED INITIATION INVENTORS ems" A]. 5//w'a n N m N m b A fl MW H0 M United States Patent 3,326,125 faEQ UlENCED lNlTliATliNA TECHNIQUE FOR XlPLGSii/E WAVE fiHAlPllNG Denis A. Siivia, King George, and Herbert D. Adams and David D. Abernathy, Fredericksburg, Va., assignors to the United States of America as represented by the Secretary of the Navy Filed Sept. 20, 1965, Ser. No. 488,826 1 Claim. (Cl. 102-23) Alll TRACT 0F THE DKEECLQSURE A technique for causing the detonation front, initiated from an irregularly-shaped homogeneous explosive mass, to arrive simultaneously at all points on the surfaces of the mass.

The invention described herein may be used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to explosives and more particularly to a method of explosive wave shaping.

Generally, the mechanism of explosion involves a chemical exothermic reaction. When a homogeneous mass of a high explosive material is initiated at one point, the resulting detonation front travels uniformly through the charge as an expanding sphere. In the case of a centrally initiated spherical charge the detonation front would, therefore, arrive simultaneously at all points on the surface of the sphere.

However, in the case of a centrally initiated irregularly shaped charge, the detonation front initially forms as an expanding sphere until the portion of that surface of the charge nearest the point of initiation is reached. Thereafter the detonation front travels through the remainder of the charge as an expanding segment of a sphere until the entire explosive mass is consumed.

Accordingly, if it is desired to centrally initiate an irregularly shaped charge while providing simultaneous detonation of the surface thereof, some means mus-t be utilized to control or shape the expanding detonation front Within the charge. In the past, the most widely accepted method of accomplishing this has been by the use of inert barriers interposed at selected locations within the explosive charge so as to control the rate of expansion of the detonation front therein. This method is more fully illustrated by US. Patent Nos. 2,999,458 and 3,016,831, both of which are issued to D. L. Coursen.

Another prior art technique for accomplishing the same result has been through the use of a plurality of different explosive compositions, each having a different detonation velocity, combined into a single explosive charge. By appropriate positioning of the different explosive compositions within the explosive charge, for example, by placing the explosive compositions with higher detonation velocities at the minimum depth locations and the explosive compositions with the lower explosion velocities at the maximum depth locations, the surface of an irregularly shaped explosive charge can be made to detonate simultaneously.

Although such prior art devices have served the purpose, they have not proven entirely satisfactory under all conditions of use since they inherently become rather complicated and thereby expensive as the geometrical complexity of the explosive surface increases.

The general purpose of this invention, therefore, is to provide a method of explosive wave shaping which embraces all the advantages of similarly employed prior art methods and devices and which possesses none of the 3,326,l25 Patented June 20, 1967 aforedescribed disadvantages. To attain this, the present invention utilizes a plurality of detonators which are sequentially initiated so as to provide simultaneous detonation of the surface of an explosive charge having any geometrical shape.

Accordingly, an object of the present invention is the provision of a method of explosive wave shaping.

Another object is to provide a method of explosive wave shaping wherein simultaneous detonation of the surface of an irregularly shaped explosive charge may be accomplished.

A further object of the invention is the provision of a method of producing an explosive plane wave.

Still another object is to provide explosive wave shaping in a homogeneous mass of explosive material without the use of any inert barrier materials.

Yet another object of the present invention is the provision of a method of explosive wave shaping which is characterized by simplicity of construction, low cost and ease of operation and use.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:

FIG. 1 is a side elevation view, partly in section, of one embodiment of the invention; and

FIG. 2 is a perspective view, partly in phantom, of another embodiment of the invention.

The present invention accomplishes explosive wave shaping by placing a plurality of detonators within a homogeneous mass of explosive material and by initiating the detonators in a known sequential relationship to one another according to their respective distances from the surface of the explosive material. For example, if the explosive charge is cone shaped, a plurality of detonators would be spaced along the axis thereof extending from near the base to a point near the apex. Since the detonator near the base of the cone would be the furthest from the surface thereof, it would be initiated first while the remaining detonators would be initiated in a sequential manner thereafter with the timing between each successive detonator being dependent upon the dimensions of the charge. In determining the time delay between successive initiations the formula Ah AL-Vzi wherein At is the time delay, Ah is the differential distance in height between the surface of the charge adjacent the first detonator and the surfaces of the charge adjacent the remaining detonators and V is the detonation velocity of the particular explosive composition utilized. Of course, this formula assumes that the explosive charge is sym metrical about the detonators. If it is not desirable or possible to utilize either a symmetrical explosive charge or to place all of the detonators along an axis thereof the above formula must be utilized somewhat differently. Assuming that it is desired to obtain a plane wave simultaneously at the surface of an irregularly shaped explosive charge, the distance Ah in the above formula would be computed as the difference between the distance that the detonator furthest away from the surface of the charge is and the respective distances that each remaining detonator is from its adjacent surface. These differences would then be utilized in the above formula to obtain the relative firing order of each of the respective detonators.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 an explosive charge, generally indicated by reference character 10, comprised of a homogeneous mass of explosive composition 12 in the shape of a barrel having a plurality of annular ridges therearound. The particular explosive composition utilized is not critical as long as it is homogeneous. For example, such explosives include, among others, PETN, RDX and HMX. As is illustrated in the drawing, the central ridge 14 having an annular surface 16 is of a greater height than the two equal side ridges 18 and 20 having annular surfaces 22 and 24, respectively. The remaining annular surfaces 26, 28, 30 and 32 are of substantially equal height with respect to the axis of the charge 12. A plurality of spaced detonators D D and D are disposed within the explosive charge 12 such that each one is in radial alignment with one of the aforementioned annular surfaces. A control box or timer 34 is connected through leads 36, 38 and 40 to the detonators D D and D for selective initiation thereof.

The operation of the embodiment illustrated in FIG. 1 will now be set forth with respect to obtaining simultaneous detonation of surfaces 16, 22, 24, 26, 28 30 and 32. As is apparent, the detonator D is initiated first since it is in alignment With the ridge 14 and is, therefore, the greatest distance from the surface of the charge 12. The detonators D being in alignment with the second largest ridges 18 and 20, would be initiated simultaneously after a predetermined time lapse from the initiation of detonator D The detonators D being in alignment with the surfaces 26, 28, 30 and 32, would be simultaneously initiated a predetermined time lapse after the initiation of detonators D and D In determining the aforementioned time lapse between the detonation of detonators D and D and D and D the formula would be utilized wherein At is the time lapse between initiation of the various detonators, Ah is the differential height between the respective annular surfaces adjacent each of said detonators and V is the detonation velocity of the particular explosive composition utilized. Suppose, for example, that the particular explosive composition has a detonation velocity of 15,000 feet per second and that Ah is equal to 3 inches and Ah is equal to inches. Substituting these values in the above formula for both Ah and Ah and solving for At gives At equal to 16.7 microseconds and At equal to 27.7 microseconds. That is, if detonator D is initiated at a time zero, then in order to simultaneously detonate surfaces 16, 22, 24, 26, 28, 30 and 32, detonators D would be initiated 16.7 microseconds after the initiation of detonator D and detonators D would be initiated 27.7 microseconds after the initiation of detonator D Of course, it is necessary to utilize an extremely accurate detonator mechanism in order to initiate the various detonators at precisely the exact time. It has been found that the series spark gap detonator, as disclosed in US. patent application Ser. No. 286,138, filed June 5, 1963, by W. L. Gilbertson et al., is completely satisfactory for this purpose.

A second embodiment of the present invention, as illustrated in FIG. 2, comprises a substantially hemispherical mass of explosive composition 42 having a convex upper surface 44 and a planar lower surface 46. A single detonator D is disposed near the center of the upper convex surface 44 while a plurality of detonators D are disposed in a circular array around the periphery of the charge 42 near the surface 46 thereof.

If, for example, it is desired to simultaneously detonate the lower planar surface 46, the detonator D would be initiated first and then, depending upon the detonation velocity and the dimensions of the particular charge utilized, all of the detonators D would be simultaneously initiated a predetermined time period after the initiation of detonator D The formula At d would again be utilized to determine the exact time lapse between the initiation of detonator D and detonators D It is understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that many modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claim.

What is claimed is:

A method of explosive Wave shaping comprising the steps of:

forming an explosive charge into a configuration having an axis of symmetry and surfaces of varying distances from said axis;

placing a plurality of detonators within said charge along said axis of symmetry with each detonator associated with a respective one of said surfaces; and initiating said detonators in a predetermined sequential relationship depending upon the distance of each of said surfaces from said detonators, whereby a simultaneous detonation of all of said surfaces is obtained.

References Cited UNITED STATES PATENTS 2,856,850 10/1958 Church et al 102-24 FOREIGN PATENTS 1,287,806 2/1962 France.

BENJAMIN A. BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner. 

